Method for hydrocracking high molecular weight hydrocarbons



F. J. JENNY Aug. 1o, 1965 METHOD FOR HYDROCRACKING HIGH MOLECULAR WEIGHT HYDROGARBONS Filed May 19, 1960 m. w n m FRANK JT TENA/Y United States Patent 3,200,061 ME'EHD FR HYDR'CRAQKENG HEGH M- LECULAR WEEGHT HYDRCARBNS Frank J. `lenny, 460 W. 24th St., New York 1l, NX.

' Filed May i9, 1960, Ser. No. 30,725

2 Claims. '(Cl. 208-53) nous coals and heavy, high sulphur tars, to form gasoline fand other valuable, normally liquid hydrocarbons.

There is a large and ever-growing interest in methods of increasing the value of primary fuels, that is, in upgrading them. Competition among the coal, natural gas and petroleum industries is increasing and methods of converting primary fuels of low cost into more valuable forms are being avidly sought. Specic interest is being Ydirected more to the relative cost of the B.t.u. and less to cost per unit of weight Ior volume of the primary fuel. Frequently, fuels may be interchangeably employed. A properly designed and equipped utility installation for generating electric power should be operable either with solid, liquid or gaseous fuels. In such case, the choice of the fuel which is to be employed is controlled by the current economic conditions in the three competing fuels. The object always sought is the maximum number of B.t.u.s for the fuel dollar.

The market value of a fuel, furthermore, is not cornpletely governed by the cost of its production. In a locality adjacent a coal producing area, the market price of coal is easily competitive with natural gas, which must be transported hundreds of miles by interstate pipelines. Coal, furthermore, in a coal producing region is competitive with petroleum fuel oils, which must be transported either by tank car, pipeline or truck. When, however, coal must be transported appreciable distances, the cost of coal transportation, when added to the cost of the product at the mine, makes the price of coal prohibitive.

It will be clear that a method which can upgrade coal to the form of a liquid or gaseous fuel will reduce the cost of transportation per B.t.u. of the fuel and create a new market outlet for coal.

It is to be noted, further, that currently this country has reached a transition point from being a net exporter of petroleum products to being a net importer of them. This change is apparently due to the comparatively high cost of producing domestic crude oil. An additional and major factor is the large and constantly growing demand and the almost profligate consumption of higher grade petroleum products. Besides this, the long range availability `of high quality crude oils is becoming increasingly less. Accordingly, there has been, and is, a pressing need for an economically and commercially feasible process which will convert heavy crude oils, and particularly those having a high sulphur content, into economically more valuable and more generally utilizable hydrocarbons. The diculty of processing the sro-called high sulphur tars makes them in large supply. Neither these nor bituminous coal are readily moved by pipeline, as are the high quality crudes.

It was pointed out in my copending application Serial No. 369,900, tiled Iuly 23, 1953, that high molecular ice Vthe sensible heat of the hotsynthesis gas which is freshly generated and passed intothe hydrocracking zone; second, by the admissionr of oxygen into the hydrocracking zone so that some of the carbon formed in the hydrocracking zone is immediately `burned to provide heat.

The third mode of supplying heat disclosed in my copending application is that of preheating the charging stock in an atmosphere of hydrogen to prevent the formation of carbon deposits.

One object of my invention is to .provide `an improved method for upgrading `primary fuels and particularly those inthe range of heavy sulphur tars, bitumens, bituminous coals, tar sands, oil shales and the like.

Another object of my invention is to provide a'novel and improved method for converting heavy, hydrocarbons having low hydrogen-to-carbon ratios intomore desirable gaseous and liquid fuels by hydrocracking in'a novel, expeditious, convenient and' economic method.

A further object of my invention is to provide -a novel method of supplying heat tothe hydrocrackingzone. K

A further lobject of my invention is to provide a process for converting primary fuels to more valuable fuels in which higher yields of the desired liquid fractions are obtained than heretofore achieved.

Other and further objects Vof my invention will appear from the following description.

ln general, my invention contemplatesthe establishment of a iluidized or free flowing bed of char or c-oke from which a stream of char is constantly withdrawn for external heating by combustion of a portion `of the char with an oxygen-bearing gas, such as air or the like. The superheated char is returned to the bed and may be superiheated in its passage by the addition of oxygen as part of the transport gas. The bed of char is maintained in heated condition by the flow of freshly formed, hot synthesis gas, that is, a freshly formed mixture of carbon monoxide and hydrogen. The hydrogen in the heating gas furnishes the hydrogen `atmosphere for the hydrocracking step. The heavy hydrocarbons charged to the process are introduced into the fluidized bed of char. These hydrocarbons may be preheated bythe use of oxygen for controlled oxidation ofa portion of the charge. Advantageously, if the charge is normally solid or supercooled liquid, such as bituminous coal, the commnuted charge is admixed with an appropriate selective solvent, preferably one formed in the process.

The synthesis gas generator in my process acts as a scavenger, taking only the lowest grade residue fuels. High-grade gasoline and distillates are economically formed by my process.

'Ilhe .accompanying drawing which forms par-tof the instant specification 1and which -is to be read in conjunction therewith is .a diagrammatic view showing one Iform of apparatus capable of carrying out the process of my invention.

More particularly, referring now to Jthe drawing, the charge, which may be `any heavy hydrocarbon, `such as properly pulverized bituminous coal or the like, from.

any appropriate source, passes through pipe -10 in fluid flow. iI-t is known to the tart that commnuted materials will act `as liquid-s, if confined in a pipe or the like and yfed infsmal-l quantity of -a gas. The charge is pumped by 3 pump =1`2 through a mixing zone 214 in-to which a selective solvent passes through pipe '16. The hydroaromatic hydrocarbons, such as tetr-alin, decalin and other hydrocarbon fractions yformed in the process, are appropriate solvents. The solvent, Iwhich is .thus antecedent-ly formed in the process, may be withdrawn from the bottom of frac- ,tionating tower l18 through pipe 20, past valve 2.2 and pumped by pump 2-4 through pipe 26 into pipe .16. If

desired, solvent from any suitable source (not shown) .may be pumped by pump y28 through pipe 30 .past valve ,32 into pipe 16. The solvent and the coal are thoroughly mixed by any appropriate means known to the art in .the mixing zone 14. The quantity `of solvent which is mixed with the coal may vary. The quantity is regulated ,to obtain substantial solubility of desired lighter fractions of the charge in the solvent. Thus, the `fraction of coal dissolved may vary from about 15% to 50% of the charge. With charging stocks having conventional petrolleum characteristics, such as heavy high sulphur tars, the .percentage solubility of the char-ge may be up to as high as 80% to 90%.

Depending upon the particular solvent used 'and the temperature at vvhichthe solution. is effected, the weight of the solvent will vary Ibetween vvlde limits. lIn a .typical case, as much as twice the Weight of ,solvent with respect to the weight of charge may be employed. l

As contemplated, the use of a selectlve solvent results in a higher yield of upgraded liquid product. In the `processing of heavy `oil liquid fractions ywhich are very viscous, the solvent increases the tuidity of the charge.

high molecular Weight compounds comprising the solid fuel. By immediately subjecting these dissociated high molecular Weight fractions to an atmosphere of excess hydrogen, further hydro-depolymerization occurs with resultant increased volatility and impro-ved overall liquid yields. lCor-respondingly, partial hydrogeneration of the very highly unsaturated fragments is simultaneously eiected which prevents repolymeri'zation of s-uch fractions. 'Thus there is bot-h a decreased lower overall net yield of coke or char, `and correspondingly a higher liquid yield of upgraded distillate fractions.

With high molecular. weight hydrocarbons, such as bituminous coal, .as the -ooal is pre-heated, it passes through a plastic temperature range during which itV becomes very viscous and is rendered non-susceptible to conventional Vpreheat for all practical purposes. "In a similar manner, lheavy petroleum fractions 'will deposit coke on the vvalls vof a preheater tube which will eventually clog .the tube and prevent further flow. This situation is aggravated lay the temperature gradient required .across the metal of the heater tube, which temperature gradientis necessary lto effect heat ow into the hydrocarbon fraction being preheated. The hydrocarbon"ffilm temperature immediately adjacent the vvall of the metal heater tube will be fappreciably greaterthan the average hydrocanbon temperature in thatV section of the tube, thus inherently accelerating .the formationof coke. This coke clings to 'the metal Wall .and builds up Va permanent laye-r of colte. The charge is usually rich in gum-forming compounds which Ihec-ome manifest in the plastictemperature range. These gummy substances, if not properly counteracted, will preclude yand prevent the formation of the Iiuidizedbed which I'desire in my process owing to the fact that the gummy substances'v will simply coa-lesce the coal 'particles and dest-roy the =finely divided form necessary lfor lluidity. lny order to preheat the charge and to selecvmonoxide and hydrogen.

i Y tively -burn off or oxidize gummy substances, I introduce oxygen int-o the preheating Zone 34. The oxygen is taken from any suitable source (not shown) .and passed through pipe 36, through pipe 38, past valve 40, into the oxidizing or preheating zone 34. It is to 'be understood, of course, that the oxygen is under lany appropriate superatmospheric pressure enabling it'to be charged to the process. The oxygen may be substantially pure, if desired. Or it may be as low yas 40%'in purity. iIt will be appreciated that the purer the oxygen, the lower will be the quantity of inert gas which must be passed through the system and eliminated. Sucient of the charge is oxidized to preheat the charge to a temperature as high as 850 F., if desired. Preferably, I heat the incoming rCharge to a temperature in the vicinity o-f between 500 F. and 6009 F. The temperature of preheat is governed, on one hand, by the quantity of gum-forming compounds in -the coal. I desire to remove these -by conversion in order to be able to maintain a fluid .bed inthe reaction zone. On the other hand, the temperature of preheat is vgoverned by the ,amount of solubility desired.V Generally Ihigher solubility ratios, that is, the percento-f the charge to lberlissolved, ,require a higher preheat temperature. The preheated charge passes throughpipefl?r into the hydrocraclsing zone 44.

A gas rich in hydrogen, removed from the absorber 46, is pumped by compress-or 48 through pipeline 50,

through pipeline `52, past valve 54, through pipe 56 to the vtransfer pipe I58, through which hot synthesis gas lfrom the synthesis gas generator 60 passes into hydrocracker 44.

I may introduce a low-grade carbonaceous fuel from any'appropriate source through pipe 62, past valve 64, through pipe 66 in to the syntheisis gas generator. it is to be understood, of course, that a portion of the waste gas flowing out` of pipe 68 may be introduced through p ipe 62 to the synthesis gas generator.V At the ysame time, I may introduce a portion of the uidized char Withdrawn from the hydrocracker into the synthesis gas generator through. transfer pipe 70 controlled by valve 72. Oxygen from pipe 36 is introduced into the synthesis gas generating zone within the synthesis gas generator 60 through pipe 74 under the control of valve 76. The generation of synthesis gas proceeds yat temperatures above l500 F., advantageously between 1800 F. and 3000" F. It will lbe understood, of course, that any ash formed in the synthesis gas generation zone, as would be 4the case when coal is charged to they process, may be removed through the pipe 61 by opening valve 63. The

`control of the oxygen supply controls the temperature.

Steam from any appropriate source ilows through pipe .78, through pipe S0, past valve S2, through pipe 84, and

thence through the pipe 66 into the synthesis gas generator. The steam thus introduced with the portion of the charge will react with carbon to produce a mixture of carbon The hot gases generated in the synthesis gas generator furnish'a portion of the heat of hydrocracking and, at the same time, supply the hydrogen atmosphere-for the hydrocracking step. It will be observed thatessentially we have` a high-temperature oxidation occurring inthe synthesis gas generation zone.

Another portion of the char passes through conduit 86 under the control of valve 88. If desired, excess char .may be withdrawn from the system through pipe 90 under the control of valve 92. Any appropriate gas may be introduced into the conduit S6 through pipe 94 to maintain the char in flowable condition. In thismanner, the char is withdrawn from the hydrocracker and passed into a char-heating zone 96 where a portion of kthe char is consumed by Voxidation to heat the char.

' portion of the hydrocracked reaction products.

aandoet if .3 The char may be heated to temperatures as high as 900 F. to 1500 F., if desired. I prefer, however, to heat the char to between ll F. and 1300" F. In order to maintain the char in a tluidized condition and to provide the impelling gas to return the char to the fiuidized char bed within the hydrocraclcer 44, 1 may bleed a portion of the air from pipe 98 to pipe 102 under the control of valve 104 and introduce this air into the transfer duct 106 which returns the heated char to the hydrocracking zone. In order to provide an atmosphere of hydrogen, I introduce steam from any appropriate source through pipe 108, past valve 110 into the transfer duct 106. This will permit the conversion of some of the carbon into a mixture of carbon monoxide and hydrogen by reaction of the steam with the carbon of the char. Besides this, the steam helps aerate the returning char. In order to provide the heat for the endothermic reaction of the conversion of carbon and steam into a mixture of carbon monoxide and hydrogen, I introduce oxygen through pipe 112 under the control of valve 114. This oxygen may further heat the char and maintain it in highly heated condition for introduction into the hydrocracking zone at temperatures between 900 F. and 1500 F., and preferably between 1l00 F. and 1250i" F.

In order to maintain the temperature of the hydrocracker between 800 F. and 1500c F., with a preferred temperature range in the vicinity of 850 F. to 1300 F., I controllably introduce steam and oxygen into the hydrocracking zone. Steam from pipe 78 flows through pipe 116 under the control of valve 118. If the temperature gets too high, an excess of steam will reduce the temperature owing to the endothermic nature of the reaction of carbon with steam. If the temperature gets too low, the introduction of oxygen from pipe 36, through pipe 120, under the control of valve 122, will increase the temperature within the hydrocracking Zone owing to the exotherrnic nature of the oxidation of either the coke, the heavy coke-forming hydrocarbons or other components.

The overhead product leaving the hydrocracker 44 through pipe 124 is cooled in heat exchanger 126 by heat exchange with any appropriate medium passing through pipe 128 and being withdrawn through pipe 130. The cooled overhead products comprise a mixture of various hydrocarbons including gasoline, distillate and some heavy hydrocarbons, as well as hydrogen, carbon monoxide, entrained carbon and some normally gaseous hydrocarbons. A great many of the fractions contained inthe overhead product are especially susceptible to hydrogenation. Accordingly, some or all of the reaction products may be withdrawn from pipe 132, through pipe '134, under the control of valve 136 and passed to a hydrogenation apparatus, indicated by the reference numeral 138. Any appropriate hydrogenation process known to the art may be employed. For example, the hydrogenation process shown -in U.S. Patent 2,674,634 may be advantageously used to hydrogenate all or a The hydrogenated product is removed from the hydrogenation zone through pipe 140 and passed through pipe 142 to he fractionating tower 18. Recycle hydrogen for the hydrogenation step is supplied from the gases withdrawn from the absorber 46 through pipe 68. Accordingly, a portion of this hydrogen-bearing gas, which is being recycled to the hydrocracking zone, is withdrawn through pipe 144 under the control of valve 146 and passed to the hydrogenation zone as the hydrogen used in the hydrogenation process.

Normally, all or a portion of the reaction products from hydrocracking zone pass through pipe 148, under the control of valve 150, into pipe 142 and thence into the fractionating tower 18.

Recirculation of the hydrogen-bearing gas to the hydrocraclrirug zone permits an independent selection of the operating pressure while maintaining a low partial pres- '6 sure of the reacting hydrocarbons. This facilitates the depolymerization reactions. As disclosed in copending application Serial No. 369,800, now abandoned, an intermediate hydrocarbon stream may then be withdrawn from the fractionating systemv to be recycled to the hydrogenation step for hydrogenation. A suitable stream would be recycled bottoms taken from the fractionating tower 18. The presence of an excess of hydrogen in the hydrocracking zone facilitates a partial sulphur reduction of high-sulphur hydrocarbon fractions by the maintenance of a high hydrogen partial pressure. This aids and abets conversion of the fmercaptans and other sulphur compounds into hydrogen sulfide. Besides al1 this, the recirculated hydrogen gas fractions act as a carrier gas to ensure substantially completely stripping of the solvent vapors.

Where the quantity of hydrogen effectively produced in the synthesis gas generator 60 and in thev transfer tube 106 is not adequate for over-all process requirements, the lower grade hydrocarbons removed from the bottom of the flash tower may pass through pipe 152 under the control of valve 154 and be pumped by pump 156 `past valve 158, thence into pipe 84 to the 'synthesis gas excess flash-tower bottoms may -be recycled to the incoming charge.

The Valve maintains the fractionating tower 18 under a predetermined pressure. Thevhigher boiling hydrocarbons removed from the fractionating tower 18 through pipe 20, which are not recycled by pump 24, pass by valve 164 through pipe 162 into the flash tower 150 and are flashed into vapors and heavy, normally liquid fuel oil-like hydrocarbons. The fuel oil flash tower improves Ithe eiliciency of the separation to a degree not obtainable in the fractionating tower and aids in the complete removal of the lighter, more economical, valuable hydrocarbons. The top of the flash tower is maintained at a predetermined temperature by reux condensate pumped by pump 166 through pipe 168, past valve 170, through pipe 172 to the top of the tower 150.

'The bottom of the flash tower is maintained at a predetermined temperature by steam introduced through pipe 174 under the control of valve 176. The gases and 'vapors withdrawn from the top of the ash tower by pipe are cooled in condenser 182 which is supplied with a cooling medium through pipe 184 under Ithe control of valve 186. The condensate -is withdrawn from the condenser 182 through pipe 188 and passed into a separator from which any residual gas may be vented through pipe 192. A portion of the normally liquid hydrocarbons boiling within the distillate range is recycled as redux condensate, as just pointed out. The balance of the distillate is withdrawn through pipe 194 under the control of valve`196 and passed to storage (not shown).

The distillate will be found to be especially high in aromatic hydrocarbons owing to the fact that the hydrocracker was operated at a preferred temperature of about 1100 F. This distillate, therefore, contains hydrocarbons which are especially valuable as a solvent for the heavy hydrocarbons being charged to the process. Accordingly, I may recycle a portion of the distillate through pipe 198 by opening valve 200, thus permitting the distillate to pass into pipe 26 and thence into pipe 16 for admixture with the hydrocarbons being charged to the process.

The normally gaseous hydrocarbons and vapors and normally liquid hydrocarbons are withdrawn from the top of the fractionating tower 18 through pipe 202 and flow past valve 160 through pipe 204 through condenser 206 which is supplied with a cooling medium by pipe 208 under the control of valve 210. The condensate leaves the condenser 206 through pipe 212 and ows into a separator 214. A pump 216 pumps a portion of the condensate through pipe 218, past valve 220 for introduction to `the top of the fractionating tower as reflux condensate. The balance of the condensate flows past valve 222 through pipe 224 into a stabilizer tower 266. The bottom of the stabilizing tower is maintained at a predetermined temperature by reboiler 267 supplied with a heating medium through pipe 268 under the control of valve 270. The vapors which comprise light hydrocarbons and normally gaseous hydrocarbons are withdrawn from the top of the stabilizer through pipe 272 and pass through a condenser 274 which is supplied with a cooling medium through pipe 276 under the control of valve 278. The condensate leaves the condenser 274 through pipe 28@ and passes to a separator 282. Any

normally gaseous products are Withdrawn from the separator through pipe 234 under the control of valve 286. A portion of thek condensate is pumped by pump 28S through lpipe 290 under the control of valve 292 to the top of the stabilizer tower 266. The balance of' the light hydrocarbons are withdrawn from the separator through pipe 294 under the control of valve 296. The stabilized gasoline-like hydrocarbons are withdrawn from the bottom of the stabilizer 266 through pipe 300 and pumped by pump 302 through a cooler 304 which is supplied with a cooling medium through pipe 306 under the control of valve 303. The cooled condensate comprising the desired gasoline is withdrawn from the cooler 304 through pipe 310 and passed to kstorage (not shown). A portion of the stabilized gasoline passes through pipe 312 and is pumped by pump 314 through pipe 316 to the top of the absorber 318 as the lean liquid menstrum. The gases and vaporsV withdrawn from the separator 214 through pipe 320 are introduced to the bottom ofthe absorber 46 'for upward countercurrent contact with the lean menstrum. The enriched stabilized gasoline is withdrawn from the bottom of the absorber through pipe 322 and pumped by pump 324 into the stabilizer 266 through pipe 224 along with :the condensate from separator 214.

VThe normally gaseous hydrocarbons, the hydrogen,` the unreacted carbon monoxide and any inert gases are withdrawn from the top of the absorber through pipe 328 past valve 330 and either vented to the atmosphere or recycled through pipe 50. This recycle hydrogen acts as a carrier gas toensure substantially completely stripping of the solvent vapors in the reaction zone. As previ- Cil ously recited, the gas vented from pipe 68 may be passed l to a synthesis-gas generatorfor conversion of the gaseous hydrocarbons. It will be understood to those skilled in the art thatsynthesis gas can be converted to hydrogen art.

It will be `observed that I have accomplished the objects of my invention. I provide a novel and improved process for the conversion of high molecular weight hydrocarbons having a low hydrogen-to-carbon natio, such as bitumin-ous coals, heavy high sulphur tars and .the like, to form gasoline and other valuable, normally liquid hydrocarbons. -I establish a bed of fluidized or free flowing char in a hydrocnacking zone into which the hydrocarbons to be cracked 4are introduced. I circulate the char from the hydrocracking zone toa char heater and back to the hydro- 1cracking zone. In the low-temperature heating of char, the carbon is converted int-o .a mixture of carbon dioxide .rand steam which is vented from the stack of the char .consumption of some of the .Char for purposes of supplying of any desired purity by procedures well known in the heat to the reaction zone may be accelerated. This selective combustion occurs owing to the fact that heavy hydrocarbons with the highest carbon-forming tendencies have the lowest initial combustion temperatures and therefore will be the first to react with the oxygen which is directly added to the charge through pipe 3S. The oxygen introduced through pipe into the hydrocracker will have a like selective oxidation effect on the lowest grade hydrocarbons present in the hydrocracking zone. It will beseen that I employ oxygen as an extremely useful fuel, introducing it into the process in five different places. There has always been a psychlological` prejudice in the art t0 the investigation ofthe use of oxygen as a process tool. It must be carefully controlled since the reaction with the highly combustible hydrocarbons and oxygen israpid and active. The temperature at which oxygen is introduced must be such that' it willlimmediately react and thus serve its intended purpose. `The use of oxygen prevents the formation of gum-forming compounds which will prevent the formation of a fluid bed. It will be observed that the charging stocks comprising the heavy hydrocarbons to which my process is peculiarly adapted have low hydro- -gen-to-carbon ratios and cannot, .accordingly,'be cracked by methods known to the prior ar-t to produce desired gasoline-like hydrocarbons. I correct the deficiency Iin hydrogen in Vmy proc-ess in two ways. fFirst,I reduce the carbon by the hydrocracking process in the presence of an excess of hydrogen. Besides this, I add hydrogen to the overhead products removed yfrom the hydrocracker in a separate -hydrogenation zone. Owing to the low hydrogen-to-carb'on ratio, -an excess of carbon is formed in the process. This carbon is converted into the synthesis gas and into heat and recycled to the process. Thus, I correct the deficiency by increasing the hydrogen-to-carbon ratio in the desired product andeliminlating the excess carbon as coke or char. When the process conditions are correctly adjusted, suicient carbon may be eliminated so that the only hydrogenation which is needed in the hydrogenation zone will be a mild one which will aromatize the hydrocarbons formed in the process, aid in gum removal and in the removal :of sulphur in the form ofrhydroge'n sulde. It is to be understood, of course, that if a high sulphur tar is 'being charged to the process, the gases removed from the absorber may be passed to a hydrogen sulfide removal step (not shown) before recycling. By my process the lowest grades of primary fuels are economically converted into more valuable, lower-boiling liquid hydrocarbons. It is to be remembered, however, that the etliuent from the hydrocracking zone contains lall of the'necessary components for hydrogenation. The vaporized distillate present inthe eliluent has fractions of a lowhydrogen content. The eiiluent contains hydrogen which is present in the unreacted synthesis gas. Ths mixture can readily be converted in hydrogenation apparatus to a primary fuel of ya specification grade distillate. I prefer to hydrogenate -a portion of the reactor effluent since the heavier of the normally liquid, unsaturated hydrocarbons formed in the process will repolymerize in liquid phase if not hydrogenated. It will also be observed that the hydrogenation ordinarily -occurs at a lower temperature than the hydrocnacking step so that it will not be necessary to reheat .the eiiluent from the hydrocracker on its way to the hydrogenation zone.

It will also be' observed that the distillate formed in the yprocess is especially suitable as a solvent for the heavy hydrocarbons being char-gedto the process and may be conveniently recycled to eiect substantially selective solution of desired components. yIt will, of course, be under- -stood that the use of other solvents is also contemplated. Such other solvents include the classification of parafins, and preferably isoparaflins which react chemically with the highly unsaturated fragments of the cnacking reaction to form new and useful compounds by alkylation and other `condensation type reactions. The recycling ofra hydrogenrich gas to the reactor facilitates an additional degree of Spooner freedom in operating the process. This recycle H2 may be of any desired purity consistent with the activity of the specific hydrogenation catalyst used in the hydrogenation process. Pressure is not critical and `any appropriate pressure may be employed for the operation of my process. The heat of the reaction is maintained prefenably by a `selective oxidation of carbonaceoussolids. `My process yis continuous. After I establish `a circulating ring of char lfrom the 4Huid char bed to the char heater and back to the hydrocracking zone, the amount of char which is bled from this circulating ring to the `synthesis gas generator will depend on process conditions and the proportion of excess carbon in the charging stock. Heavy hydrocarbons formed in the process are recycled to the reactor where they may be effectively hydrocracked.

I have provided an improved method for upgrading primary fuels, and especially those in the range of heavy sulphur tars, bituminous coals, tar sands, oil shales and the like, for which no economically feasible cracking process lis provided by the prior art. I have provided an improved method for converting heavy hydrocarbons having low hydrogen-to-carbon ratios into more desirable gaseous and liquid fuels. My hydrocracking method for heavy `hydrocarbons includes la unique mode of supplying heat to the hydrocracking Zone.

Advantageously, I upgrade the hydrocracked distillate fractions from the hydrocracking stage by a second stage reaction. These distillate fractions are conveniently hydrogenated to produce normally liquid fractions of improved product quality.

'F or this second stage reaction, I may also employ other methods for producing normally liquid fnactions of improved product quality. Thus, the solvent used -in my hydrocracking .stage is vaporized an-d carried to the second stage. By employing suitable -alkylating temperatures, pre-ssure-s and catalysts, condensation products are formed with hydrocracked unsaturated fractions to form premium quality liquid fuels.

As desired, depending upon the particular high molecular weight hydrocarbon being hydrocracked, I may also use la catalytic reforming, or hydroforrning stage, as my second stage reaction. In practicing hydroforming, where dehydrogenation reactions may predominate in the conl@ version of saturated and cyclic hydrocarbons to .aromaticS, the excess hydrogen serves as a source of hydrogen for the hydrocracking reaction process. Suitable hydroforming and `alkylation or condensation type process are known in the art.

IIt will be understood that certain features and subcombinations are of utility and may be employed with-out reference to other features `and subcombinations. This is contemplated by and is within the scope of my claims. It is further obvious that various changes may be made in details within the scope of my claims without departing from the spirit of my invention. It is therefore to be understood that my invention is not to be limited to the specic details shown and described.

I claim:

1. In ya process for the conversion of hydrocarbons wherein a hydrocarbon is subjected to cracking in a cracking zone in the pre-sence of a substantial flow of a free hydrogen containing gas, the improvement of upgrading hydrocracked fractions which comprises withdrawing hydrocarbon vapors and hydrogen from said cra-cking zone, lsubjecting said hydrocarbon vapors and hydrogen to reaction in a hydrogenation Zone at effective hydrogenation temperatures and pressures .and in the presence of `a hydrogenation catalyst, separating the products of hydrogenation into vapor and liquid fractions, and recovering -a hydrogenated liquid hydrocarbon.

2. A process as in claim 1 in which said cracking includes coking and in which said cracking and coking reactions occur in contact with a fluidized bed of coke particles.

References Cited by the Examiner UNITED STATES PATENTS 2,207,494 7/ 40 Viktora 208-107 2,391,793 6/ 44 Voorhees 208-7 2,913,388 111/58 Howell et al 208-8 2,917,451 !l2/ 5 9 Leler 208-107 ALPHONSO D. SULLIVAN, Primary Examiner.

ALLAN M. BOETTCHER, MILTON STERMAN,

Examiners. 

1. IN A PROCESS FOR THE CONVERSION OF HYDROCARBONS WHEREIN A HYDROCARBON IS SUBJECTED TO CRACKING IN A CRACKING ZONE IN THE PRESENCE OF A SUBSTANTIAL FLOW OF A FREE HYDROGEN CONTAINING GAS, THE IMPROVEMENT OF UPGRADING HYDROCRACKED FRACTIONS WHICH COMPRISES WITHDRAWING HYDROCARBON VAPORS AND HYDROGEN FROM SAID CRACKING ZONE, SUBJECTING SAID HYDROCARBON VAPORS AND HYDOGEN TO REACTION IN A HYDROGENATION ZONE AT EFFECTIVE HYDROGENATION TEMPERATURES AND PRESSURES AND IN THE PRESENCE OF A HYDROGENATION CATALYST, SEPARATING THE PRODUCTS OF HYDROGENATION INTO VAPOR AND LIQUID FRACTIONS, AND RECOVERING A HYDROGENATED LIQUID HYDROCARBON. 